Tube-forming mechanism.



R. KOENIG.

TUBE FORMING MECHANISM.

APPLICATION FILED MAR. 20, 1911.

1,019,968, Patented Mar. 12,1912.

COLUMBIA I'LANOGIIAPII co.,WA5H|NnTON, u. c.

UNITED STATESETENT OFFICE.

ROBERT KOENIG, OF BROOKLYN, NEW YORK, ASSIGNOR TO PI-IENIX TUBE COMPANY, OF BROOKLYN, NEW YORK, A CORPORATION OF NEW JERSEY.

TUBE-FORMING- MECHANISM.

Specification of Letters Patent.

Patented Mar. 1.2, 1912.

Original application filed.v July 27, 1910, Serial No. 574,076. Divided and this application filed March 20,

T 0 all whom it may concern:

Be it known that I, ROBERT Kermit a citizen of the United States, and resident of Brooklyn, in the county of Kings and State of New York, have invented new and useful Improvements in Tube-Forming Mechanism, of which the following is a specification.

My invention relates to the construction of prismatic sheet metal tubes and consists in mechanism for making such tubes.

The object which I have in view is to make prismatic metal tubing which though formed with a butt-seam, without welding or swaging, shall present the appearance of a seamless tube, be amply strong for light structural purposes, and cheaper than welded, swaged or seamless drawn tubes. The method of making such tubes and the articles of manufacture which result from the performance of this method form the subject of an application for Letters Patentof the United States Serial No. 574,07 6, filed July 27, 1910, of which this application is a division.

The structural condition presented by a butt-seamed, sheet metal tube having longitudinally disposed narrow regions of inter nal stress may be, and I believe is best, produced by compressing the tube at intervals around its periphery, between dies or rollers on the one hand, and an internal mandrel on the other, so that the metal flows slightly in both directions out of the compressed regions, each local flow meeting an oppositely directed flow proceeding from an adjoining region of compression. The meeting place of these two opposed flows of metal thus becomes a region of internal strain which when the tube emerges from the restraint of the instruments which formed it, holds the two edges of the seam tightly pressed together, producing an apparently seamless tube, instead of the openseamed tube which would otherwise result from the operation of the residual elasticity in a tube simply rolled up in the manner heretofore practiced. Such a tube will be in a substantial sense prismatic, although the number of locally strained longitudinal narrow regions may be so large that the tube when finished is nearly cylindrical, so nearly so that a coat of enamel will produce apparently true cylindricity.

In particular, however, my invention has Serial No. 615,542.

for its object the production of obviously prismatic tubes, and will be adequately understood from a description of the method of forming a square tube, of the instruments used to carry out the method, and of the structure of the tube itself.

A concrete example of my invention is illustrated in the drawings hereto annexed, in which Figures 1 to 1 represent diagrammatically three preliminary stages of the manufacture of a prismatic tube out of flat sheet metal; Fig. 2 represents, partly in cross section, on a larger scale, the instruments for forming a square tube, and the tube therein; and Fig. 3 represents in perspective on a small scale, a piece of finished square tube.

I have found it desirable for practical purposes to form a cylindrical tube of sheet metal as a preparatory step toward the final construction of a prismatic butt-seamed tube. This preparatory step is illustrated in Figs. 1 to 1 inclusive, Fig. 1 showing a cross section of a strip of metal which is to be formed into the tube. This strip will have been cut with shears which leaves a projection or bur indicated at b along the cut edges on one side of the strip. For purposes presently to be explained, I so place the strip of metal in the bending machine that when the cylindrical tube is formed, the burs lie on the outside. The formation of the cylindrical tube involves a rolling and drawing in any of the well known machines suited to the purpose, which first shapes the tube in channel form having a rounded U section as indicated in Fig. 1 and then further rolls and draws the metal so that the cylindrical tube shown in cross section in Fig. 1 is the result. The mandrel and die which give the final cylindrical shape to the metal bring the two edges of the strip close together, but when the residual elasticity of the metal causes the two edges of the seam to spring apart slightly leaving a gap such as shown at g in Fig. 1 The cylindrical, open-seam tube is then placed in the machine which is to convert it into a prismatic tube with a closed butt seam.

For purposes of illustration, I take the case of a square tube to be made from the round tube above described. A draw-bench machine such as used for squaring seamless drawn tubing, will serve my purpose, with changes in the mandrel and roller dies, as hereinbelow described. The tubes or instruments in the machine for forming the square tube which immediately perform the work, consist of an internal mandrel marked M in Fig. 2 and a roller die or former composed of four external rolls R which are opposed to the sides of the mandrel. This mandrel is held in position by a rod M which is laid in the cylindrical tube of metal and is anchored outside the end of the tube to a convenient portion of the frame of the drawing machine. The forward end of the tube is gripped by the traveling aws of the drawing machine in the usual manner. The arrangement of four rolls which constitute the external former or die is in general the same as that shown in Figs. 1 and 2 of Carrs United States Patent No. 402,140, and the positional relationship of the mandrel and sheet metal tube to each other and to the rolls is much the same as that shown in Fig. 1 of Ostranders United States Patent No. 113,332. The mandrel M and rolls R operate upon all portions of the metal tube except at and near the corners of the prism which is formed by the rolling and drawing operation. Thus the edges of the rolls R as shown in Fig. 2, are well inside of the salient angles of the square tube and the edges of the mandrel M are chamfered 01f at the corners at m, so that the active pressure and drawing friction is exerted on the inside by the sidesmof the mandrel M and on the outside by the rolls R. The provision of clearance between the operating instruments at the corners thereof or rather at the places where the salient angles or edges of the tube are formed, together with the heavy pressure brought to bear between the mandrel and the rolls bends and compresses the metal of which the round tube was formed and which is being squared in the machine, at the sides of the squared tube, and this causes a flow of the metal of which the tube is composed from the sides toward the angles, the direction of this flow being indicated by the arrows in Fig. 2. Therefore at each corner C of the square tube the flow of metal coming from two directions produces a region which is set in compression at each salient angle of the tube; these compression regions are indicated conventionally by heavy shading at the points G in Fig. 2. The dimensions of the mandrel M and rolls R are properly adapted to the peripheral dimensions of the round tube shown in sec tion at Fig. 1 so that in forming the prismatic tube the edges of the gap 9 are brought together. But when the prismatic tube has been formed as above described, the presence at the salient angles of the tube of regions in which the metal of which the tube is formed is under internal compressive strain produces a resultant of contractile effort as contrasted with the residual expansive elasticity manifested in the round tube shown in Fig. 1 and the edges of the seam at g are held in close mutual abutment. As the burs .7) were left at the outside of the tube, these are rolled into the seam 9 so as to fill the slight irregularities due to imperfect cutting of the strip in the first place.

Butt-seamed prismatic tubes formed as above described present to the eye the appearance of seamless drawn tubes and are amply strong for many light structural purposes, such as the manufacture of metal bedsteads or other furniture, and by reason of the simplicity of their method of manufacture,

can be made more rapidly and cheaply thanseamless drawn, brazed, or welded tubes. Close scrutiny of a prismatic tube formed as above described may detect the butt seam, but as metal tubes of this kind will usually be coated, painted or enameled, the butt seam will entirely disappear from view in the final product.

WVhat I claim and desire to secure by Letters Patent is:

1. In a machine for making prismatic butt-seamed tubes, the combination of an internal mandrel and an external former both provided with clearances at the places where the salient angles of the tube are formed.

2. In a machine for making prismatic buttseamed tubes, the combination of an internal mandrel chamfered at the corners and external rolls each cooperating with a side of the mandrel and affording external clearances corresponding in position to the chamfered corners of the mandrel.

Signed by me at Brooklyn, N. Y. this fourteenth day of March 1911.

ROBERT KOENIG.-

Witnesses:

G. M. WHEELER, GEO. H. MEARs.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

